Page 85: of Maritime Reporter Magazine (September 1999)

Making Noise

The study of shipping generated noises effect on the environment is a relatively new phenomena, but it is sure to become increasingly important in the new decade.

While shipboard noise is an obvious concern to personnel operating or luxu- riating onboard, increasing attention is being paid to the effects of ship-generat- ed noise on the ocean environment.

Consequently, this should catch the attention of ship designers, builders, owners and outfitters as the topic inevitably starts making the conference and legislative rounds. Headlining efforts in the U.S. is the National

Resources Defense Council (NRDC), whose researchers are studying the effects of man-made undersea noise and its relationship to a healthy ocean, and its effects on certain types of marine

Buquebus: Sound Reduction

Advances

The effort to eliminate sound and vibra- tion signatures is particularly critical in the passenger/cruise vessels markets for many reasons. A noisy, shaky ride is sure to alien- ate passengers and hurt business prospects, but adding layer upon layer of sound-dead- ening materials adds critical weight factors and effectively reduces a vessel's profitabil- ity as well. In creating the 52-knot Buque- bus, builder and designer took extra steps to ensure that noise control was judiciously yet adequately placed. Sound measurement trials were completed with noise measure- ments taken by noise consultants, J & A

Enterprises Inc., at various locations throughout the vessel with the microphone held at approximately five ft. above sole. At an early stage in the design, NGA and

Derecktor decided to pursue a philosophy of not fitting any sound insulation, other than the inherent sound deadening provided by fire insulation, until noise measurements could be completed during trials. This sim- ple approach allows for noise reduction to be applied exactly where it is required, with a potential saving in the weight of addition- al noise insulation that may not have been effective. Average noise levels within the lower and upper passenger saloons during initial trials were 82 db(a) and 76 db(a) respectively. This trial also showed noise generated from the hull bottom with the vessel at high speed (I 15 db(a) in forward voids) was contributing significantly to the interior noise levels. Therefore, following this trial, two forms of noise reduction were installed. Polymer panels were applied to areas of the bottom structure to provide mass damping of these panels and secondly, a layer of sandwich construction insulation with a high-density middle layer was applied across the underside of the deck in way of the passenger saloon. The combined effect of these treatments was to reduce the average noise level in the lower deck pas- senger saloon to 75 db(a) and to 72 db(a) in the upper deck saloon. species. Undersea noise has reportedly been shown as affecting the habitual behavior of marine mammals; leading them to swim off course, abandon tradi- tional breeding grounds, and cease from singing, clicking, and performing the patterned sequences of sound, experts believe, they use for communication in the depths of the ocean. "The amount of noise in our oceans nearly doubles every 10 years," says

Roger Jentry the coordinator for the

National Marine Fisheries Service (NMFS) Acoustics Team. According to a recent report put out the NRDC, the largest producer of undersea noise is shipping. NRDC statistics reveal that since the on-set of the global economy, the size of the merchant fleet has dou- bled and gross tonnage quadrupled engrossing shipping lanes and the ocean's lower frequencies with constant noise. The same lower frequencies existing research has shown marine species use to interact in. In 1996, two sperm whales swimming nearby Spain's

Canary Islands were struck from behind and killed by a cargo ship. Investiga- tions believe that neither one made any attempt to escape the ship's path.

Reports say, both whales were suffering from low-frequency acoustic trauma in the inner ear and apparently did not hear

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